High-frequency dielectric heating apparatus



Aug. 16, 1949. R. H. HAGOPIAN 2,479,351

HIGH-FREQUENCY DIELECTRIC HEATING APPARATUS Filed Aug. 10, 1945 Tube Oscillator G ene/"a for Tub e Oscillator Generator WITNESSES: INIVENTOR ATTORNEY Patented Aug. 16, 1949 UNITED HIGH-FREQUENCY DIELECTRIC HEATING APPARATUS Richard H. Hagopian, Halethorpe, Md., assignor to Westinghouse Electric Corporation,

Pittsburgh, Pa., a corporation of Pennsylvania Application August 10, 1945, Serial No. 610,067

9 Claims. 1

This invention generally relates to dielectric heating, but is more particularly directed to improved means and methods for dielectrically heating long cylindrical shapes of dielectric material such, for example, and not in limitation, as large rolls of paper stock.

It is an object of my invention to provide means for controllably heating long cylindrical dielectric material in an elongated electric field having field lines transverse to the length, or axial, direction of the material.

It is a primary object of my invention to provide a means through which dielectric material in the shape of rolls or the equivalent can be uniformly dielectrically heat-treated.

It is a specific object of my invention to provide a dielectric heating means for uniformly heating long, thick rolls of paper.

A further object of my invention is to practicably dielectrically heat rotating rolls of dielectric material, using axially arranged electrodes, one of which may form a core of the roll or be associated with a shaft for rotating the roll; this central electrode being at ground potential so that problems of insulating it are avoided.

Other objects, features, innovations, combinations and methods attributable to my invention will be discernible from the following description of an embodiment at present preferred, which is to be taken in connection with the accompanying schematic drawing, in which:

Figure l is a sectional view of apparatus in accordance with my invention showing in a general, but not necessarily accurate way, the electric field lines produced in the apparatus; and

Fig. 2 is a horizontal plan view thereof perpendicular to the section plane of Fig. 1.

Referring to the drawing, the material to be heat-treated is shown as a roll 2 of paper which is solidly spirally wrapped on an inner fiber core 4, and has an outer surface 6 and ends 8 and It; the roll being elongated in the direction of its axis so that it cannot be conveniently or practicably dielectrically heated by electrodes parallel to its ends 8 and I0. The roll 2 is supported for rotation on a metal mandrel or shaft I2, being fixed thereto in any suitable manner as for example by wedging means I3. The shaft I2 extends beyond the ends 8 and III of the paper roll 2, and has one end geared to an electric motor I I which, when energized, causes the roll to rotate about its axis. The rotation may be either clockwise or counterclockwise with respect to Fig. 1. The shaft I2 constitutes an electrode means, and may be grounded in any 'mannerthrough its supporting bearings, but it is shown as grounded through a brush I6 which presses on the shaft and is connected to ground, indicated at I8.

Radially outward from the roll 2, I provide an axially extending electrode means 20 and an axially extending electrode means 22 along opposite sides of the paper roll 2.

The electrode means 20 and 22 are circumferentially spaced. from each other and relatively insulated. In the particular embodiment being described, each of the electrode means 20 and 22 spans about 90 degrees or somewhat more of the surface 6 of the paper roll 2. The electrode means 20 is insulated. from the shaft i2, while the electrode means 22 is connected. in this embodiment, through a conductor 24, so as to be at the same potential as the shaft.

For providing the electric fields necessary for heating the paper roll 2 as it is rotated by the motor I4, I provide a tube-oscillator generator 26 delivering power to a coaxial output cable 28 comprising an outer conductor 30, and an inner insulated conductor 32. The former is grounded as indicated at 34, and the latter is connected to the electrode means 21) so that the last is at a high frequency potential with respect to the shaft I2 and the electrode means 22.

When the tube oscillator generator 26 is operating at radio or high frequency, an electric field is established having a component between the metal shaft I2, functioning as a central electrode, and the electrode means 28. This field portion extends radially through a sector of the paper roll 2, as indicated by field lines 31. Electric field components are also established which extend between the electrode means 20 and the electrode means 22. In effect, two fields are formed which pass directly through the paper roll 2 on opposite sides thereof, one of these fields being represented by 3.3 and the other by 39. In general, it may be said that the intensity of the electric fields 38 and 3% in the outer part of the roll nearer the surface is much greater than it is at the inner periphery of the roll, near the fiber core For Want of a better term, I call the fields and by this also meaning that the fields are more intense at the outer portions of the roll, and have field-lines which generally pass transversely through the material. By controlling the curvature and position of the electrode means 26 and 22, the outer fields and their intensities in the material 2 can be altered. However, the radial electric field is necessarily of greater intensity near the inner periphery of the paper roll than it is near the outer surface 6. By suitably adjusting the radial and outer field components it is possible to improve the uniformity with which the paper roll will increase in temperature throughout as it is heated.

In order to provide for ready adjustability of the fields, the electrode means and 22 are preferably made in a plurality ofsections permitting both radial and circumferential adjustment. Thus in Fig. 1 the electrode means 22 comprises a fixed metal U-shaped member 40 having turned edges 42 at the ends. of. its legs. In.- terlinked with each of the curved edges 42 1s a curved edge 44 of a curved metal electrode section 46 can be swung toward or away" from the-- surface 6. The electrode means 20 is similarly constructed except that its outer electrode sections 50 are formed of two slidably engaging-por tions 52 and 54 for permitting adjustment of the cincumfierential: extent of the electrode means: It. should. of course; be: understood that I have shown the electrode means in. a simplified manner;. but.they can take: any form or shape which permits. their radial and. circumferential positions witharespect to the surface 6 to bechanged, either along their full lengths. or breadths or along parts thereon.

The-strengthof the :radial field at the fiber core can also becontrolled by selecting a suitable diameter for the shaft 12. However, I. am not limited to the use oi the shaft, which rotates therolkasthe central electrode. Obviously, many other expedients-suggest themselves asa boundaryfor-the-electric field. at the inner periphery or nearthe: inner periphery of the. paper-roll 2.

While I have described my invention briefly so that: it. may be:zunderstood, it is obvious that. it is -subject toside modification and. its teachings can be: incorporated in different ways.

I clairm as my invention:

1. Apparatus ford-ielectri'cally heating cylindrical 'di'electric material, comprising, instructural combination, a central electrode means, a first outer'plate-type electrode means radially spaced and insulated" from said central electrode means; a second outer plate-type electrode means rad-iaily spaced f'rom' said central electrode means and circum-ferentially spaced and insulated from the first" outer electrode means, and energizing means connected to said electrode means for establishing an alternating radially-directed electric field between said central electrode means and said first outer electrode means; and for establishing an alternating outer electric-field on each of the opposite sides ofsald central electrode means, extending between said first and second outer electrode means.

2'. Apparatus for dielectricall'y heating cylindrical dielectric material; comprising, in. structural combination, a central electrode means, .a first. outer electrode meansradially spaced and insulated from said central electrode means, a secondiouterelectrodemeans radially spaced from said central electrode means and circumferentially spaced and. insulatedv from. the first. outer electrode: means, energizing means for establishing an. alternating. radially-directed electric field between said: central electrode means and said first outer-electrode means, and for establishing analternati-ng outerelectric'field on each side of said central elect-rode means, extending; between said: first and secondouter electrode means, and 7 for rotating said. material, said central electrode means and said second outer electrode means being grounded.

3. Apparatus for dielectrically heating elongated cylindrical dielectric material having a central axis, comprising, in structural combination, an electrode means centrally of the material, a first curved plate-typeelectrode radially spaced from said central electrode means, a second curved plate-type electrode radially spaced from said central electrode means and circumferentially spaced from said first curved electrode, at least one of said pair of curved electrodes extending circumferentially on both sides of a plane including said axis and the curved electrodes, means. connected for applying a high frequency voltagebetween said central electrode means and said first curved electrode, means connected for applying a high frequency voltage between said first and second curved electrodes whereby to establish radial and outer alternating electric fields in said material, and. means. for rotating said material about said central electrode means and in the space between said central electrode means and: said. curved electrodes.

4, Inapparatus for heating an annular article of dielectric material, the combination of. a first electrode, a second. electrode spaced: therefrom whereby said. electrodes are adapted to receive said article therebetween. with its axis parallel toelectrodes, a third! electrode within said article, said first and third electrodes being electrically connected toeach. other for maintenance thereof at the same potential, and means for coupling said electrodes to-a source of high frequency electrical energy for producing between said second electrode and each of said first and third electrodes a high frequency electric field for generating heat in said article.

5. In apparatus for heating elongated dielectric material wound. on an electroconductive core to constitute. an annular. package, the combination of a pair of electrodes arranged in opposed, spaced. relation toeach other for. the reception of said packagetherebetween with the axis of said core parallel to. said electrodes, means electrically connecting said core to-one' of' said pair of electrodes whereby said coreand saidone electrode are' maintained at the same electrical potential, and means-for coupling said electrodes and said core to-a source of ltigh frequency electrical. energy for producing between the other of. said pair oi electrodes and each of said core and said one electrode a high frequency electric field for gen-- erating heat insa-id material.

6. In apparatus for heating an annular article of dielectric material, the combination of a pair of electrodes disposed to-receive. said articletherebetween with the. axis of saidarticle parallel to said electrodes, a third electrode within said article cooperatively related to said pair of. electrodesand means for maintaining said third electrade and one of said pair ofelectrodes at the sameelectrical potential.

7. In apparatus, for. heating an annular article of dielectric material; the combination of a pair of electrodes: arranged in opposed, spaced rel-ationto'each other for. the reception of said-article therebetween with its axis parallel tosaid electrodes, and a third electroclewithin said article cooperatively related to said pair of'electnodes; said third electrode being electrically connected to one of said pair of electrodes for maintaining saidone electrode .and said third electrode at the same: potential,

Apparatusaccording:tosclaimFlt-characterized by the addition of means for rotating said article substantially on its axis.

9. Apparatus for dielectrically heating elongated dielectric material having a central axis, comprising, in structural combination, an electrode means centrally of the material, additional electrode means radially spaced from said central electrode means, said additional electrode means comprising an insulated first curved portion and a second curved portion, said central electrode means and said curved portions extending longitudinally, one of said curved portions having a concave face facing said axis which is circumferentially less than 180, and lies on both sides of a plane which includes said axis and passes through both of said curved portions, the last said curved portion having axially directed edges circumferentially spaced from corresponding edges of the other of said curved portions, and means for applying a high frequency voltage between said insulated curved portion and said central electrode means, and between said first and second curved portions.

RICHARD H. HAGOPIAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Modern Plastics, June 1944, page 111. 

